What causes this variable clutch to be a bit abrupt when its in the cold warm up cycle but work perfectly when warm?

From my understanding there isn't an issue with the stepped lockup clutch hot or cold, it is just left open to help heat the engine and gearbox.

The older on/off design could feel a bit strange, if you didn't know what was happening. In fact some have commented it even felt it was another gear, when the 5-speed would engage the lockup in 5th, and revs would drop a few hundred revs.